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<?php
session_start();

$userinfo = array(
                'admin'=>'admin',
                'user2'=>'password2',
                'Kek'=>'Lol'
                );

if(isset($_GET['logout'])) {
    $_SESSION['username'] = '';
    header('Location:  ' . $_SERVER['PHP_SELF']);
}

if(isset($_POST['username'])) {
    if($userinfo[$_POST['username']] == $_POST['password']) {
        $_SESSION['username'] = $_POST['username'];
    }else {

    }
}
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
        "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <meta charset="utf-8">
    <link rel="stylesheet" type="text/css" href="../css/sign.css">
    <link rel="stylesheet" type="text/css" href="../css/bootstrap.min.css">
    <title>Login</title>
</head>
    <body>

        <?php if($_SESSION['username']): ?>
            <h2 class="yomama" ">Результат</h2>
            <h2 class="yomama"><a href="?logout=1">Logout</a></h2>

        <?php endif; ?>


<form name="Login" class="form-signin" action="" method="post">
               <input type="text" class="form-control" name="username" placeholder="Username" required="" autofocus="" value="" />

              <input type="password" class="form-control" name="password" placeholder="Password" required="" value="" />
            <input class="btn btn-lg btn-primary btn-block" type="submit"
            value="Submit" />

        </form>
    </body>
</html>